For your choir’s 20 minute recital, you have free choice: just remember that you have 20 minutes to fill, and that the organ may not have much in the way of registration aids. For Evensong, the repertoire needs to be appropriate to a liturgical situation. For Evensong, you can perform: Introit (optional), Responses (which could be sung to plainsong, or said), Psalm (you can choose the psalm, up to the full BCP psalmody for the day; again this could be sung to plainsong or said), Canticles, Anthem, Hymn (optional).
In order to make sure there are no surprises, we ask that you provide, at the point of registration, a rough sense of the repertoire you might perform. This can be finessed and finalised later in the year, but the extra time allows us to help and advise you if necessary. It’s totally fine to repeat repertoire from Evensong in the recital, of course!